1. Field of the Invention
This invention relates to a cylinder block of an internal combustion engine, arranged to lower the noise level of the engine.
2. Description of the Prior Art
As a cause of engine noise, there is vibration noise emitted from a so-called cylinder block skirt or lower section and an oil pan which noise is caused by the vibration of a cylinder block. In order to reduce such vibration noise it seems enough to suppress vibration, due to explosion torque, applied to a crankshaft by increasing the rigidity of the cylinder block. However, this unavoidably leads to an increase in cylinder block wall thickness and accordingly to a great increase in engine weight, thereby giving rise to new problems such as a deteriorated fuel economy. In view of this, a variety of propositions have been made to improve the rigidity of the cylinder block while suppressing the increase in cylinder block weight.